Integumentary system

The primary role of the integumentary system is

protection

Dermatology

study and treatment of the integumentary system: the skin(integument), hair, nails, and subcutaneous glands.

skin

largest organ of the body

There are two layers of skin

The epidermis and the dermis

Epidermis

• Keratinized stratified squamous epithelium

  • superficial layer

  • thicker on acral skin

  • avascular (nutrients diffused from deeper connective tissue)

  • sparse nerve endings

cells in the epidermis

• Keratinocytes

• Stem cells

• Melanocytes

• Tactile (merkle) cells

• Dendritic (langerhans) cells

Keratinocytes

• synthesize keratin (found in many layers)

  • make up about 90% of cells in the epidermis, arise from the deepest layer and are actively dividing cells, these cells move upward towards the apical surface , they are no longer dividing and are dead, dry, and full of keratin

Stem cells

• Divide and produce keratinocytes (Stratum Basale)

Melanocytes

• manufacture and secrete a pigment called melanin in response to the skins exposure to the suns harmful UV rays (stratum Basale)

  • Pigment is stored in melanosomes which move melanin along the melanocyte until the granules are passed onto the neighboring keratinocytes

  • melanin forms a shield in order to protect keratinocytes from damage response is commonly known as sun tanning.

  • darker skinned people naturally have more, darker melanin which their keratinocytes can retain longer, compared to lighter skinned people. The excess production of melanin is a direct result of our skins exposure to the sun and why it makes sense that darker skinned people would burn less and experience skin cancer less frequently.

Tactile (merkle) cells

• touch receptors that join with nerves (only in stratum basale) (present at epidermal-dermal junction, part of sensory reception function of the skin)

Dendritic (langerhans) cells

• cells that work in a protective capacity by activating our immune system and by ingesting any foreign particles that may have penetrated the barrier. (in stratum spinosum and stratum granulosome)

Layers of the epidermis

• mnemonic (Before, Signing, Get, Legal, Counsel)

  • Stratum Basale: is the deepest layer of the epidermis and is attached to the underlying dermis , only one layer thick, has varied cell types)

  • Stratum Spinosum: several cell layers thick (8-10 cell layers), thickest layer of the epidermis.

  • Stratum Granulosome: cells have dark granules, (1-5 layers thick, nuclei being to disintegrate and cells begin to die as they move to the layers above)

  • Stratum lucidum: Only in thick skin, cells lack organelles

  • Stratum Corneum: uppermost or apical layer, composed of several layers of dead scaly skin (25-30 layers) filled only with keratin.

    • these cells continuously shed and are familiar to us as dead skin or flakes and dandruff.

Dermis

• second layer of skin found deep to the epidermis

  • dermis is made of connective tissue

  • rich in collagen fiber (partly where skin gets it flexibility, loss of collagen causes wrinkles)

  • contains cutaneous glands, hair follicles, arrector muscles, and nail roots.

The dermis is made up of two layers

• Papillary and Reticular layer

Papillary layer

• Nipple shaped, superficial (upper) thin layer, made up of areolar connective tissue, it makes up about 20% of the dermis. Like areolar connective tissue the papillary layer contains WBC (macrophages and mast cells) and fibroblast

  • the wavy finger like projections called dermal papillae anchors the epidermis to the dermis which increases the surface area , it also increases the surface area for gas, nutrients, and waste exchange between the layers.

Reticular layer

• About 80% of the dermis, deepest layer, made up of dense irregular tissue, contains blood vessels to nourish it, as well as thick collagen fibers.

  • Extreme stretching of pregnancy or obsesity can tear collage fibers the result is pink or white scars known as stretch marks (Striae)

Hypodermis

• not a true layer of the skin, it is located deep to the dermis and contains adipose (subcutaneous fat) and areolar tissue. Function is energy storage, thermal insulation, and connection to deeper tissue.

Thick skin vs thin skin

• thick skin (acral): palms, front of fingers, soles, plantar toes. hairless, no sebaceous glands, sweats. Adaptive for high friction.

• Thin skin: covers most of body. hairy, has both sebacous glands and sweat glands.

Functions of the skin

• Waterproof: protects us against water loss

• Resistance to trauma and infection:

  • contains melanocytes which protects us from harmful uv rays

  • contains thick bands of collagen which protects us from scrapes and external penetration by sharp objects.

  • Produces secretions which destroy bacteria on surface

• Thermoregulation:

  • when too hot blood vessels dilate allows heat to be carried to blood stream and dissipate through skin.

  • when too cold blood vessels constrict in order to maintain heat within the body and divert to vital organs.

  • Synthesis of Vitamin D : When skin is exposed to sunlight Vitamin D precursors is formed, which is sent through the blood stream to the liver and kidney to be converted into vitamin D. Vitamin D plays a role in absorption of calcium which is needed for bone growth and development.

  • Sensation: sensory receptors in the skin keep us aware of the conditions occurring at our body surface.

  • Nonverbal communication: conveys emotions, health statuses, and physiological responses without using spoken words. Body language.

Diagnostic of skin color

• Cyanosis: Blue; lack of oxygen

• Erythema: red; increased blood flow

• Pallor: pale or ashen; reduced blood flow

• albinism: white genetic lack of melanin

• jaundice: yellow; liver and bilirubin

• Hematoma: purple; bruised

skin markings

• Friction ridges of fingertips: Aid in sensitivity to texture and ability to grasp, cause finger print patterns. Because of the presence of sweat glands along with these ridges we can identify prints on everything we touch.

• Flexion lines (creases): Where skin near joint attached to deeper tissue

• freckles: flat, melanized patches, vary with heredity and uv exposure

• Mole (nevus): Elevated patch of melanized skin, beauty marks.

• Hemangiomas (birthmarks): discolored skin, caused by benign tumors of capillaries.

Hair

• is an accessory organ of the skin. It is also known as pilus (singular) and pili (plural)

  • are made of hard keratin which does not allow for the flake off, making the structure more durable .

  • hair is produced by hair follicles, which is extended deep into the dermis or even hypodermis.

  • hair grows on most thin skin (exceptions include: lips, nipples, parts of genitals, and distal segments of fingers.)

  • the hair matrix contains a single row of actively dividing cells as these cells are pushed farther away from the matrix by the production of new cells the cell starts to die and fill with keratin

  • the hair shaft is the part of the hair where keratinization is complete located just above the hair root and is the part of the hair that is visible through the skin.

    • split ends are sometimes seen at the end of the shaft which is essentially the splitting of 3 layers from each other due to the wear and tear our hair undergoes daily.

  • melanocytes also line the dermal papilla within the hair bulb along the hair matrix the pigment produced is filtered into the cortext and depending on the color of melanin produced will impact your hair color.

  • as we age melanine production declines and is replaced by air bubbles in our hair shaft resulting in hair that is white or gray in color.

Three types of hair

• Downy hair (lanugo): fine, downy, unpigmented hair of fetus.

• Vellus hair: is the fine body hair found on adult females and children (unpigmented) (not the eyebrows, eyelashes, or scalp)

• Terminal hair: is the darker hair comprising our eyebrows, eyelashes and scalp. After puberty the male sex hormone stimulates further growth of terminal hair on our genital region, underarms (axillary region), male facial hair, chest, some hair on trunk and limbs.

Hair grows in 4 stages

anagen (growth phase), catagen (follicle shrinks and detaches from hair papilla), telogen( hairs are in this stage at any one time), and exogen (hair detached and sheds)

What is the difference in cross section between curly and straight hair?

• Straight hair is round in cross section

• curly hair is flatter

Nails

• are made up of hard keratin, derivatives of stratum corneum, composed of very thin, dead, scaly cells with parallel rows of keratin, primates have flat nails.

  • nails are use to grab onto things, scratch things, and pick up things.

There are 3 major parts to a nail

• nail plate, nail fold and nail bed

what structure make up the nail plate

• consists of 3 main parts

  • free edge: the portion of the nail that extends beyond the finger tip

  • nail body: the main visible part of the nail attached to the nail bed

  • nail root: the part of the nail hidden under the skin at the base

nail fold

• the nail fold: refers to the skin that overlaps the nail at its base and sides.

• the nail grove is the actual indentation or channel created by this fold.

  • these structures are important for proper nail growth and health

nail bed

• Nail bed: The skin beneath the nail plate; contain blood vessels and nerves.

  • Hyponychium: area under the free edge of the nail.

  • Nail matrix: the tissue that produces the nail plate

  • Lunule/lunula: the visible cresent-shaped whitish area at the base of the nail.

  • eponychium (cuticle): the tissue that overlaps the nail plate at the base.

Important role of cuticle

• extending onto the nail body is the cuticle (Eponychium). the proximal nail fold and cuticle form a seal to prevent bacteria from entering the nail matrix.

How does nail get it color, how does it effect circulation?

• nails get nice pink color due to presence of capillaries in underlying dermis, since nails are transparent the crimson color of the blood shows through, color of nail is used to determine quality of blood circulation. By pressing your nail on your nail plate and then releasing you can watch how quickly the color returns if nail does not return to nice pink color this may be indication of poor circulation.

sebaceous glands

• are found all over the body except for the palms of hands and soles of feet. Secrete and oily substance called sebum whose function is to collect dirt and kill bacteria on our skin, coat our skin to impede water loss, and lubricate our hair to prevent it from becoming brittle.

  • usually opens into a hair follicle

  • these glands are small on most of our body but are quite large on our face, neck, and upper chest regions.

  • sebaceous glands: are simple branched alveolar glands, however, functionally they are holocrine as once they accumulate so much sebum they burst expelling their contents onto the skin surface occasionally and hair follicle most often.

  • Acne is a result of inflammation of a sebaceous gland usually caused by a bacterial infection, result pimples, most often seen on face, can range in size and if left untreated can cause permanent scaring.

sweat glands

• Also found widely distributed over the body except for the nipples and external genitalia

There are two types of sweat glands

• eccrine and apocrine.

Aprocrine

• are found in the groin region, axilla (armpit), areola (colored region surrounding nipple), and beard.

  • Ducts open to a hair follicle

  • It is odorless until it combines with bacteria that feed onto the secretion, in which then it takes on an odor which we call body odor. (bacterial metabolism of those fats cause odor)

  • respond to stress and sexual stimulation

  • develop in puberty

  • believed to secrete pheromones

There are two other specialized apocrine glands:

• ceruminous gland: found in auditory canal. Its secretion when mixed with sebum and dead skin cells from neighboring sebaceous glands forms cerumen or what we know as ear wax.

• mammary glands: glands develop during pregnancy and lactation otherwise scant, produce milk, you can have breast but not have mammary glands not synonymous

eccrine or merocrine glands

• are the most numerous sweat glands and produce what we know as sweat.

  • widespread but most abundant in palms of hands, soles of our feet and on our forehead

  • the sweat that is secreted is 99% water with some salts, vitamins, and metabolic wastes (found in urine).

  • sweat also contains a microbe-killing peptide to help eliminate potentially harmful microorganisms on the surface of the skin.

  • Simple ducts leads to pores at the skin surface.

  • Produce watery perspiration to cool body.

  • sweating begins on forehead and palms of hands then quickly spreads over entire body

  • sympathetic nervous system kick starts glands into action

Skin cancer

• possibly one of the most avoidable types of cancer.

  • Biggest risk factor of developing skin cancer is exposure to sun’s harmful uv rays (natural) or tanning beds

  • most common to occur in elderly and fair-skinned people

three types of skin cancer

• Basal cell carcinoma

• squamos cell carcinoma

• malignant melanoma

Basal cell carcinoma

• most common type of skin cancer and least malignant.

  • slow growing, and easily removed with much success

  • rarely metastasizes

  • arises in stratum basale and invades dermis

squamos cell carcinoma

• 2nd most common type of skin cancer, arises from the keratinocytes in the stratum spinosum. Grows more rapidly and may metastasize if left untreated.

  • can metastasize to lymph nodes

  • skin discoloration becomes more apparent and is an indication of cancerous lesions

  • if caught in time and removed successfully good chance of complete recovery

  • can be fatal.

malignant melanoma

• cancer of melanocytes. Most deadly, but only in 5% of cases. Arises from melanocytes of existing mole (nevus). Metastasizes quickly and often fatal of not treated quickly.

  • Risks factors: frequent sun exposure, having lighter skin color, family history, and develops from pre-existing moles.

How to recognize melanoma (ABCDE rule)?

• A- asymmetry: examining the sides of the mole and whether they match each other

• B- boarder: do the boarders of the mole have any indentations or are they smooth

• C- color: does the mole contain a variety of colors (black, brown, tan) or the color uniform.

• D- diameter: mole larger than 6mm in diameter.

• E- evolution: is the mole changing over time.

Burns

• is caused by excessive heat, electricity, or certain chemicals, all of which cause cell damage and/or death in the affected area.

  • leading cause of accidental deaths: fluid loss leading to dehydration; Infection leading to sepsis; Toxic effects of eschar (dead tissue).

  • First and second degree burns are partial thickness burns while third degree burns are considered full thickness burns.

First degree burns

• are the least sever type of burn, only the epidermis is damaged and healing usually occurs within a few days. A sunburn is the most common type of first degree burn. Redness, pain and swelling are common.

Second degree burn

• The epidermis as well as the upper part of the dermis is damaged, often the damage destroys the connection between the two layers. along with localized pain, redness, and swelling, blisters also form (important not to pop blisters as you don’t want to introduce unnecessary bacteria into an already compromised skin wound). May damage hair follicles, nerve endings, and cutaneous glands.healing usually takes longer with a second degree burn approximately 3-4 weeks. Example sever sunburns and scalds

Third degree burns

• most sever burn, the burn consumes the entirety of the skin (epidermis and dermis) and possibly the hypodermis and underlying muscle tissue. Bones, muscles, tendons maybe affected. the burned area often looks white, bright red, or blackened and little swelling. Contracture and disfigurement can result in scarring. These burns are often dry and painless due to glands and nerve endings being destroyed. Individuals with third degree burns run risk of infection and fluid loss could lead to sever dehydration. A skin graft is needed in order to stimulate healing.

what happen when aging

• hair turns grayer thinner

• melanocytes stem cells die out

• mitosis slows down

• dead hairs not replaced

• atrophy of sebaceous glands (dryer skin)

• skin becomes thinner and more translucent

• fewer and more fragile vessels (if blood supply bad there not going to be able to sustain hair on legs)

• rosacea: dilated blood vessels that cause reddened areas

• increased bruising

• thermoregulation: vulnerability to hypothermia and heat stroke

Some disorder of the integumentary system

• acne

• dermatitis

• eczema

• psoriasis

• ringworm

• rosacea

• warts